Method of separation of phenyl-phenols



E. C. BRITTON ET AL METHOD OF SEPARATION OF PHENYL PHENOLS Filed Dec. 5, 1929 I Feb. 2, 1932.

0 0 a 0 H m 9 M W 6 m M Patented Feb. 2, 1932 UNITED STATES.

EDGAR c. BRITT'ON Ann FRED BRYNER, or MIDLAND, MICHIGAN, Assreuoas orrie v now CHEMICAL COMPANY, orMInLAnn, MICHIGAN, A'oonroRA'rroN or rcnrenu METHOD OF SEPARATION OF PHENYIi-PHENOLS Application filed December 5, 1929. Serial No. 411,760.

The present invention relates to the separation of phenylphenols from mixtures thereof, particularly to methods involving the hydrolysis of alkali metal salts of orthoand para-phenylphenols in aqueous solutlon.

Alkali metal salts of the aforesaid phenylphenols are hydrolyzed by water into. the free phenylphenols and alkali hydroxide, as represented by the equation,

' OM on o wherein M represents an alkali metal,ge. g. sodium or potassium. We have found that ency to hydrolyze than the corresponding ortho-salt so that free para-phenylphenol may be separated in relatively pure form upon dilution of an aqueous solution containing I both the orthoand parasalts before any appreciable separation of the free ortho-compound, occurs. Further, from the residual solution ortho-phenylphenol may be obtained In said annexed drawing The figure is a chart giving a curve which 0 shows the relationship between percentage composition of mixtures of-ortho- .and paraphenylphenols to the melting pointsthereof. By way of illustration, our method will be described below as applying to the separation of orthoand, para-phenylphenolsfrom an aqueous solution containing the sodium salts thereof. 1

Upon diluting such solution, the. concentration of alkali hydroxide therein tends to hold at a constant equilibrium value by hydrolysis the para-salt has a suiiiciently greater tendv of the metal salt into free phenylphenol and such hydroxide, asperthe above equation.

When both sodium orthoandpara-phenylphenates are in solution, as We have found,

the para-salt hydrolyzes more readily than the corresponding ortho-salt, and according-l ly, para-phenylphenol is formed preferentially and separates from the solution Again, the hydrolysis of sodium ortho: and para-phenylphenatesin aqueous solution may be controlled to any desired extent by neutralizing the free base with a strong acid as rapidly asit is formed. For instance, sufficient acid to neutralize any desired amount of base may be added to the aqueous solution of theabovementionedphe-nylphenates to ac celerate the hydrolysis and obtain a fraction: al precipitation of at least one phenylphenol. Accordingly, by controlling the extent of hy-v drolysis, e. g. by the amount of added acid,

itis possible toseparate out, firstpthe paraphenylphenol, and then the corresponding ortho-compound, with possibly an intermediate fraction containing both the orthoand para-compounds, which latter fraction may be returned to the process. 7

Further, a mixture of orthoand paraphenylphenols may be substantially separated by treating the same with aqueous caustic alkali suflicient to react preferentially with and dissolve the more acidic orthophenylphenol, the corresponding less acidic para-compound remaining substantially unattacked. In another modification, aqueous caustic alkali equivalent to all of the orthopheny-lphenol and at least a portion of the para-compound, may be used, in which case, if the mixture be heated, the alkali apparently reacts first with the entire amountof ortho: compound and then with the para-compound, and finally the phenylphenate solution thus formed apparently acts as a solvent for more or less of the remaining free para-phenylphe 1101, depending upon the proportion thereof actually present. Hence, a solution may be prepared, as described, by dissolving amixture of phenylphenols inan amount of caustic alkali insuflicient to form anormal salt with the entire amount of phenylphenols. The so-obtained solution may be treated in with an aqueous sodium hydroxide solution,

preferably to make approximately a to per cent. solution of the sodium phenylph'enates,us1ng an excess of caustic alkali to prevent hydrolysis of the sodium salts. The soobtained alkaline solution is extracted with a solvent, such as chlorobenzene, benzene, etc., to remove the abovementioned V alkali-insoluble impurities, and'then steamed, if desired, after substantial separation of the solvent,'to remove residual amounts of the latter The sodium orthoand para-phenylphenates contained in theaqueous solution may then be hydrolyzed as above described.

For the success of the process, it is advisable to known the proportion of orthoand paraphenyiphenols in the original mixture; this being found for example, by making a melting or freezing point determination on a sample of mixed phenylphenols which has been obtained upon distillation of the product obtainedby acidification of an aqueous solution of the mixed sodium salts after separa tion of the alkali-insoluble contaminants therefrom.

By comparing the obtained melting point with the melting point curve shown in the figure, the composition of the mixture may be found and utilized, for example, in calculating the amount of alkali required to combine with all the ortho-compound and a desired fraction of the para-compound also in determining the amount of acid suflicient to precipitate para-phenylphenol from an aqueous solution containing soluble salts of both the orthoand para-compounds The melting points of substantially pure orthoand para-'phenylphenol are about 57 C. and about 1667 (1, respectively.

The following examples illustrate ways in which our invention may be utilized.

Example 1.A mixture containing 6 and 4 grams, respectively, of orthoand paraphenylphenols (Mp. 123C.) was dissolved in 5.65 grams aqueous sodium hydroxide solution (29 per cent.) ,i. e. suiiicient theoretically to combine with all the ortho-compound and 25 per cent. of the para-compound prescut, at about 95 C. On coolingthe so-obtained solution to approximately 0 C., 3.6 grams ofpara-phenylphenol (hip. 165 C.) separated, i. e. the equivalent of a percent.

yield. Crude ortho-com'pound (Mp. 76 C.) was obtained from the filtrate by acidification and filtration thereof, in an amount of 5.25 grams, or an 87.5 per cent. yield. A crude intermediate fraction of 0.1 gram (Mp. 100 C.) was obtained by diluting the liquid with 50 cc. water. 1

Example 2.A mixture of orthoand paraphenylphenols, containing 60 and 40 grams, respectively, of the ortho-v and para-compounds, was dissolved in 80.6 grams of aqueous sodium hydroxide solution (29 per cent.) i. e. sufficient theoretically to combine with both phenylphenols, and 200 grams of water. To this aqueous solution, at a temperature of about 85 (1, was added-22 grams of hydrochloric acid (36.98 per cent), i. e. suflicient acid to form the free phenol from per cent. of the para-compound present in solution. After standing o'ne hour, the precipi tate was separated from the liquid by filtration thereof, washed substantially free from salt, and dried, thereby obtaining 37.6 grams of crude para-phenylphenol, having a mel ing point of 158 C. To the filtrate was added 4.63 grams of hydrochloric acid (36.93 per cent.) i. e. suilicient to precipitate the remaining 5 per cent. para-compound plus 10 per cent. of the ortho-compound whereby 9 grams of crude ortho-phenylplienol of melting point 815 C. was obtained. After separation of the latter from the solution, the filtrate was treated with more acid, thereby forming at? grams of crude product melting at 303 C. The yield of crude para-phenylphenol (Mp. 158 0.) obtained was 94; per cent. The yield of crude ortho-phenylphenol recovered was 93.3 per cent. I

()ther'ways of carrying out our invention may be utilized. For instance, it has been found that on cooling a concentrated-aqueous solution containing the sodium salts of said phe'nylphenols, there may be separated out a mixture of para-phenylphenol and the sodium salt ofthe latter, indicating conjoint hydrolysis and crystallization of the sodium salt. 7

Intermediate fractions of product contain ing appreciable amounts of mixed orthoand para-phenylphenols may be returned to the process. 7 The herein described method, accordingly, provides an industrial means for the separation of phenylphenols by means, hydrolysis of the alkali metal salts thereof in. aqueous solution. The term hydrolyzing is meant to include an accelerated hydrolysis by means of adding acid to neutralize the alkali thereby formed, e. g. preferentially precipitating the more insoluble phenylphenol by means of added acid, as well as for instance, the hydrolysis produced by diluting aqueous solutions of alkali metal salts of the phenylphenols.

Other modes of applying the principle of our invention may be employed instead of 2. The method ofseparating orthoandpara-phenylphenols, Which comprises fractionally hydrolyzing a mixture of sodium salts of such phenylphenols in aqueous solution, and removing the thereby formed solid phenylphenol at the end of each hydrolytic.

step before proceeding further.

3. The method of separating orthoand para-phenylphenols, Which comprises partially hydrolyzing a mixture of alkali metal salts of such phenylphenols in aqueous solution, separating the para-phenylphenol thereby formed, and continuing the hydrolysls.

laThe method of separating orthoand para-phenylphenols, Which comprises partially hydrolyzing a mixture of sodium salts of such phenylphenols in aqueous solution,

Separating the P -p nylphenol thereby t1 16 aqueous 1(111011.

formed, and continuing the hydrolysis.

5. The method of separating ortho-' and I paraphenylphenols, Which comprises partially hydrolyzing a mixture of alkali metal salts of such phenylphenols in aqueous solution, separating the para-phenylphenol thereby formed, and precipitating orthophenylphenol by adding acid to the residual liquid.

6. The methodof separating orthoand para-phenylphenols, which comprises partially hydrolyzing a mixture of sodium salts formed, and continuing the, hydrolysis by further addition of said acid.

9. The method of separating orthoand para-phenylphenols from a mixture thereof together With alkali-insoluble impurities, which comprises reacting such mixture With aqueous sodium hydroxide solution, extracting the so obtained alkaline solution with a Water-insoluble organic solvent to remove the above said alkali-insoluble impurities, fractionally hydrolyzing the sodium salts of such phenylphenols, and removing the thereby formed'solid phenylphenol at the end of each hydrolyt-ic .step before proceeding further.

I 10. The method of separating orthoand para-phenylphenols from a mixture thereof together With alkali-insoluble impurities, which comprises reacting such mixture With an excess of aqueous sodium hydroxide solution, extracting the so obtained alkaline solution With a relatively Water-insoluble solvent to remove the above said alkali-insoluble impurities, steaming the aqueous solution to remove residual solvent, partially hydrolyzing the sodium salts of such phenylphenols, and separating para-phenylphenols thereby formed.

11. The method'of separating orthoand para-phenylphenols, Which comprises partially hydrolyzing a mixture of sodium salts thereof in aqueous solution and separating the thereby formed para-phenylphenol from Signed by us this 26 day of November,

EDGAR C. BRITTON. FRED BBYNER.

of such phenylphenols in aqueous solution,

separating the para-phenylphenol thereby formed, and precipitating ortho-phenylphenol by adding hydrochloric acid to the residual liquid. v

7. The method ofjseparating orthoand para-phenylphenols, Which comprises pari tially hydrolyzing a mixture of alkali metal salts of such phenylphenols in aqueous solution, by adding acid thereto, separating the para-phenylphenol thereby formed, and con tinuing the hydrolysis by further addition of said acid.

8. The method of separating orthoand para-phenylphenols, Which comprises partially hydrolyzing a mixture of sodium salts of such phenylphenols in aqueous solution, by addinghydrochloric acidthereto, separating the para-phenylphenol thereby 

